The verses are in calypso form from Trinidad. The refrain is more African in nature. It may predate the verse melody. This was collected by Edric Conner for The Edric Conner Collection of West Indian Spirituals and Folk Tunes (1945). It is included in The New Oxford Book of Carols (#174). I think I learned the verses and the first part of the refrain from Jamaican singer Stan Shepherd at the Altoona Campus of Penn State.